pdf № 372, December

DOI: 10.19110/geov.2025.12.1

The hydrocarbon composition of extracts and pyrolysis products of peat from interglacial deposits of the Seida River basin, 200 ± 30 thousand years old, have been studied. To study the hydrocarbon composition, the peat extract is separated into saturated and aromatic fractions, the composition of which is analyzed by gas chromatography-mass spectrometry. The organic matter of the peat is analyzed by pyrolytic gas chromatography-mass spectrometry. The distribution of n-alkanes in the peat extracts, high Pwax and low Paq values, indicate a high contribution of woody vegetation within the studied peat section. According to palynological data, deciduous trees (Betula sp.), as well as conifers (Pinus sylvestris and Picea sp.), were widespread during this period. Triterpenoid derivatives of higher plants with oleanane and ursane carbon skeletons, markers of angiosperms, are identified in the aromatic fraction. Based on their distribution, it is established that the vegetation composition was uniform; the observed changes in component ratios are conditioned by changes in the proportions of different plant species, most likely by changing climatic conditions.

The pyrolysis products contain phenolic derivatives of the guaiacyl series, considered biomarkers of gymnosperm lignin, confirming the presence of coniferous vegetation in the peat.

The detection of n-alkenes in peat extracts may indicate the presence of lichens, and the presence of diploptene may indicate the involvement of sphagnum in peat formation.

Data on the hydrocarbon composition of the extract and the pyrolysis products of peat organic matter support palynological data indicating the presence of coniferous and deciduous pollen in the peat.

Keywords: biomarker-hydrocarbons, peat, n-alkanes in peat, peat pyrolysis products, guaiacyl phenols, aromatic triterpenoids

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DOI: 10.19110/geov.2025.12.2

The Regional unified stratigraphic scheme of Quaternary deposits of the north and northwest of the Eastern European platform, approved in 1984 and revised in 2002, needs updating based on materials on Quaternary geology and palaeogeography accumulated since then. Also updates of General Stratigraphic scale of Quaternary period should be considered. The improvement of Regional stratigraphic scheme is important due to Monitoring of State geological map of the territory and continental shelf of Russian Federation at 1:1,000,000 scale and due to geological survey at 1:200,000 scale for which a modern stratigraphic basis is required. The stages of studying the stratigraphy of Quaternary deposits in the region after 1984 are considered. Main directions of improvement of the Regional stratigraphic scheme, including of Middle Valdai interstadial and Holocene, have been proposed.

Keywords: General Stratigraphic scale of Quaternary, Middle Valdai interstadial, Holocene

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DOI: 10.19110/geov.2025.12.3

For the first time the article discusses the final stage of loess accumulation in the area of the last (Valdai, Ostashkov) glaciation in the northwest of the Russian Plain (Leningrad region). Based on data from large-scale soil mapping of the land-use area of the former Volna farm (Volosovsky district), located in the Devonian plain, three groups of soils have been identified, in the profile of which a thin (50—100 cm) mantle of subaerial sediments stands out. The granulometric groups of the soils are determined by the sedimentometric method, as well as by laser diffraction. As part of the lithomatrix of the soil profile, sub aerial al sediments form a part of the texturally differentiated profile of Holocene soils, which is light in terms of granulometric composition and enriched with a large silt fraction. The upper part of the soil profile is underlain by rocks of various genesis (tills, glaciofluvial and glaciolacustrine silty sediments, etc.). Loessoids were previously undetected in the soil profile structure. The landscape contiguity and areals of these deposits need further investigation. Aeolian sedimentation could be associated with "micro-periglacial" zones formed during the gradual retreat of the glacier. The presented factual material on the silty pebbleless sediments of the northwestern Russian Plain requires in-depth research with the involvement of specialists from related disciplines.

Keywords: loessoids, Northwest of the Russian Plain, Valdai glaciation, soils, lithogenic matrix

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DOI: 10.19110/geov.2025.12.4

The article presents results of a paleoanthracological analysis of the Kulikovo Late Glacial section (South-Eastern Baltic, Kaliningrad Region). Thr paleoanthracological analysis is proposed as a new methodological approach to study the presence of woody taxa in Late Glacial vegetation. The analysis of the samples reveal 22 macrocharcoal morphotypes, including indicators of woody (coniferous and deciduous) vegetation. The obtained results indicate an almost continuous local presence of woody species in this area since the Older Dryas (no later than ~13,980 cal yr BP). This conclusion is consistent with available palynological data, indicating that the percentage of woody taxa from the end of the Older Dryas until approximately 12.5 ka does not fall below 50 %, and over a significant part of the studied interval, it reaches 70—80 %. The paleoanthracological analysis can serve as both an independent method and an important addition to the reconstruction of Late Glacial and early Holocene vegetation based on palynological data.

Keywords: paleoanthracology, woody vegetation, palynology, southeastern Baltic, Late Glacial

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DOI: 10.19110/geov.2025.12.5

The article examines morphological features of unstudied small lakes located in the south-east of Karelia within the historic-geographical region of Zaonezhye (the Zaonezhsky Peninsula, Lake Onego). Morphology is one of the most significant features that can characterize the nature of lakes. It largely determines the functioning of lake ecosystems, influencing various lacustrine processes (hydrophysical, hydrochemical, sedimentation, etc.). Morphological features of lakes are expressed through morphometric characteristics and indicators calculated on their basis. During field studies, we conducted geomorphological and bathymetric surveys of 10 small lakes. The morphometric characteristics were determined using satellite images and topographic maps. The horizontal and vertical dissection indicators were calculated in accordance with accepted methods. It has been shown that the studied lakes are distinguished by a diversity of morphometric characteristics. This diversity explained by differences in the features of morpholithogenesis of the lakes. Four morphogenetic types of small lakes were identified of the basis on the data from previous and contemporary studies. Lake types morphometric characteristics are presented in the article.

Keywords: lake depressions, morphometric characteristics, morpholithogenesis, Zaonezhsky Peninsula, Lake Onego

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DOI: 10.19110/geov.2025.12.6

A comprehensive study of the Utinoe Boloto paleoarchive* using geochronological, lithological, palynological, and paleoanthracological analyses described vegetation dynamics and identified changes in soil erosion and fire activity during the Late Glacial and Early Holocene. The results, considered in the context of regional vegetation dynamics, allowed identifying local features likely related to anthropogenic impact. Palynological and paleoanthracological data documented the onset of colonisation of the study area through changes in vegetation cover (a reduction in tree species against a background of peak hazel and fern content) and the maximum macrocharcoal content for the section, as well as soil erosion indicators. These changes were clearly expressed within 10,300—8100 cal yr BP. Trampling of the soil cover at the site of ancient economic activity and deliberate deforestation of the surrounding area can be assumed. Elevated hazel pollen and fern spore levels, combined with macrocharcoal peaks, may indicate the burning of forest areas to stimulate the growth of hazel, one of the most important plant resources for the subsistence of the Mesolithic population. Thus, the study indicates an active interaction of ancient humans with nature and intensive anthropogenic impact on the surrounding landscape and vegetation in the immediate vicinity of the settlement already in the Mesolithic.

Keywords: Mesolithic, anthropogenic impact, paleogeography, archaeology, South-Eastern Baltic region, Kaliningrad District

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